Examples of power working machines in practical use today include those in which an operating handle is rotatably mounted on a machine body, a throttle lever is mounted on the operating handle for adjustment of an output power from a drive source, such as an engine, and a throttle lock lever is also mounted on the operating handle for locking the throttle lever. For practical use, it has been only necessary that the power working machines include, in addition to the throttle lever and throttle lock lever, a lock mechanism provided on the machine body for locking the operating handle at a desired rotational angle relative to the machine body and an operation lever dock-canceling lever) for canceling the locking, by the lock mechanism, of the operating handle. One example of the conventional power working machines is known from JP-A-11-28683, where the lock mechanism is constructed to operate in response to human operator's manipulation of a throttle wire.
FIG. 24 hereof is a view showing a fundamental construction of the conventionally-known power working machine. The power working machine 200 has a handle structure which includes: an operating handle 202 rotatably mounted on the machine body 201, a throttle lever 203 pivotably attached to the operating handle 202; a throttle lock lever 204 for locking the throttle lever 203; and a lock member 205 that is caused to project, in response to actuation of the throttle lever 203, into abutment against the machine body 201 to thereby lock the operating handle 202 at a desired rotational angle relative to the machine body 201. Namely, a user or human operator can lock the operating handle 202 against the machine body 201 by first disengaging the throttle lock lever 204 from the throttle lever 203 as depicted by arrow c1 and then gripping the throttle lever 203 as depicted by arrow c2 to cause the lock member 205 to project as depicted by arrow c3.
However, with the conventional power working machine 200, the human operator's rotating and locking operation of the operating handle 202 is very cumbersome and complicated because the human operator has to first rotate the handle 202 through a desired rotational angle relative to the machine body 201, disengage the throttle lock lever 204 from the throttle lever 203 and then grip the throttle lever 203 to thereby press the lock member 205 against the machine body 201 so as to lock the handle 202. Further, because the conventional power working machine 200 is not constructed to allow the human operator to lock the handle 202 at a desired position simultaneously with the disengagement of the throttle lock lever 204 from the throttle lever 203, the machine 200 lacks operational reliability in that trimming blades (not shown) would be undesirably activated prior to the locking, against the machine body 201, of the handle 202 depending, for example, on connection timing of a centrifugal clutch etc.
Thus, there has heretofore been a demand for an improved power working machine which allows the human operator to rotate the operating handle with simple operation and which can reliably prevent human operator's erroneous operation, e.g. by not only inhibiting or disabling human operator's operation of the throttle lever during rotating operation of the handle but also disabling rotating operation of the handle during operation of the throttle lever.